Tim:
The oil thing is like buying off a Snap On truck, Mac truck or Cornwell for tools. Some tools seem to fit your hand better than others. For some reason I bought Mac tools but SnapOn sockets. I think your preference of oil is the same thing. I've run the Amsoil for 4 years and with the analysis and what I've seen in the engine, I'll stick with it. The Series 2000 gear oil is blue. After 25K miles towing and seeing the temps go up , checking the level showed the color still to be blue. No wear metals. Still I change it every year. My engine oil, I change it every year also. About 50K miles per year. Now that is with the dual by-pass filter.
And the main thing I've found is that synthetic oil does not break down. It just gets dirty. Filter it, keep it clean and your OK.
. . Preston. .